Masonry and concrete structures are porous and are susceptible to cracking due to distortion caused by movement of their foundation, vibration, and/or drying out subsequent to their construction. In addition, below grade structures are often subjected to hydrostatic pressure from ground water. Therefore, waterproofing and sealing below grade masonry and concrete structures have been major concerns for a number of years. Masonry and concrete structures have been coated with various tar-based and asphaltic compositions. These compositions are relatively inexpensive and can be applied year-round if heated to a pliable state. However, these compositions generally contain leachable components which can contaminate the surrounding soil. In addition, these compositions contain substantial amounts of organic materials which are attacked by soil- and water-borne microorganisms and have a short useful life before decomposition to form substantial pathways through the coatings.
The most difficult questions with respect to the need for waterproofing are related to intermittent hydrostatic pressure. Intermittent hydrostatic pressure has been defined as a varied pressure gradient of short duration that will act on a wall after rain showers, induced irrigations, and snow melt.
Since this condition exists in most buildings except in extremely dry climates or extremely well-drained soils, it can be inferred that waterproofing, not dampproofing, is required for the majority of basement walls.
Numerous synthetic coatings, such as acrylic, polyurethane and rubber-based or rubberized coatings, and more elaborate waterproofing/sealing systems based on polyvinyl and polyethylene sheeting have been developed to address the shortcomings of the tar-based and asphaltic compositions. Many of the coating compositions are aqueous emulsions or latexes of the polymeric resins. The resulting films generally are short-lived as they are subject to degradation caused by soil acids and microorganisms. These compositions have generally resulted in effective application systems only when applied under non-freezing conditions. To reduce attack on acrylic coatings, including rubberized acrylic, antifungal components are often included in the compositions. However, these components can leach into the soil and may be only temporarily effective.
Rubberized coatings generally provide fragile membranes which are easily damaged and ruptured during further work and backfilling around the masonry structures and may be easily oxidized. Rubberized acrylic, water-based coatings are not effective for application at below freezing temperatures, and can suffer from microorganism attack. Other rubberized coatings include rubberized asphalt which suffers from the inclusion of organic impurities which can be attacked and decomposed by microorganisms. In addition, the rubberized coatings cannot easily be applied by brush or roller.
Polyurethane compositions generally result in unstable coatings due to plasticizer migration and exposure to sunlight to result in brittle and friable coatings. Once applied, many polyurethanes continue to evolve formaldehyde vapors which are highly undesirable. These compositions are often foamed and applied as insulating coatings.
The waterproofing/sealing systems based on polyvinyl and polyethylene sheeting generally have open seams and generally require black mastics or metal fasteners such as nails, etc., to adhere the sheeting to the masonry surfaces. The sheets are usually UV-sensitive and can be susceptible to fungus, insect and rodent attack. In addition, the sheets are difficult to form around non-uniform surfaces, and the nails puncture the sheet and will puncture cement blocks to provide a direct water channel into the interior of the block wall.
Beyond the problems discussed above, the state of the art coating compositions are generally fragile, and they must be protected during backfilling of earth around the masonry structures. Without such protection, the sheets or coatings can be ruptured, torn, pulled down along vertical surfaces by the backfill, etc. Further, many of these coating systems require that the masonry structure be dry or contain only a trace of dampness which requires careful protection of the structure before application of the waterproofing/sealing system.
Recently crystallizing waterproofing products have become available from producers such as AKONA, BONDEX, THORO SEAL and Xypex Chemical Corporation. These compositions generally are powders which include Portland cement, silica sand and other active chemicals. The compositions are applied as a slurry in water to concrete surfaces, and they penetrate cracks and pores in concrete and other cementitious structures. When the compositions cure, they generally form crystalline structures within the pores and plug the cementitious surfaces. While these compositions are generally very effective, they require careful application to perform up to their designed specifications. Careful preparation of the surfaces and the use of two or more coats of slightly different layers are necessary to ensure complete waterproofing of the structure. Due to the labor intensive application, the compositions are costly to apply. Thus these systems are of rather limited use where very high performance is required to justify the cost.
Therefore, a new, low cost, waterproof sealant is needed for use in a majority of waterproofing applications which is durable and has a long effective life span. In addition, a new method of waterproofing and sealing subterranean masonry and concrete structures is needed which is useful year round, even in northern latitudes, and which can be applied to damp masonry and concrete surfaces.
Many of the above deficiencies in waterproofing and sealing rigid structural units were overcome by applying a liquid coating composition containing a styrene polymeric resin in an organic solvent to the structural unit. On drying a film having an average water vapor permeability of less than about 1.times.10.sup.-2 perms/inch was formed. This is described in related co-pending application Ser. No. 08/258,562, now U.S. Pat. No. 5,482,737; Ser. No. 08/258,558, pending, and Ser. No. 08/315,884, now abandoned.